iothread.c

   1 /*
   2  * Event loop thread
   3  *
   4  * Copyright Red Hat Inc., 2013
   5  *
   6  * Authors:
   7  *  Stefan Hajnoczi   <stefanha@redhat.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  10  * See the COPYING file in the top-level directory.
  11  *
  12  */
  13
  14 #include "qom/object.h"
  15 #include "qom/object_interfaces.h"
  16 #include "qemu/module.h"
  17 #include "qemu/thread.h"
  18 #include "block/aio.h"
  19 #include "sysemu/iothread.h"
  20
  21 #define IOTHREADS_PATH "/objects"
  22
  23 typedef ObjectClass IOThreadClass;
  24 struct IOThread {
  25     Object parent_obj;
  26
  27     QemuThread thread;
  28     AioContext *ctx;
  29     QemuMutex init_done_lock;
  30     QemuCond init_done_cond;    /* is thread initialization done? */
  31     bool stopping;
  32     int thread_id;
  33 };
  34
  35 #define IOTHREAD_GET_CLASS(obj) \
  36    OBJECT_GET_CLASS(IOThreadClass, obj, TYPE_IOTHREAD)
  37 #define IOTHREAD_CLASS(klass) \
  38    OBJECT_CLASS_CHECK(IOThreadClass, klass, TYPE_IOTHREAD)
  39
  40 static void *iothread_run(void *opaque)
  41 {
  42     IOThread *iothread = opaque;
  43
  44     qemu_mutex_lock(&iothread->init_done_lock);
  45     iothread->thread_id = qemu_get_thread_id();
  46     qemu_cond_signal(&iothread->init_done_cond);
  47     qemu_mutex_unlock(&iothread->init_done_lock);
  48
  49     while (!iothread->stopping) {
  50         aio_context_acquire(iothread->ctx);
  51         while (!iothread->stopping && aio_poll(iothread->ctx, true)) {
  52             /* Progress was made, keep going */
  53         }
  54         aio_context_release(iothread->ctx);
  55     }
  56     return NULL;
  57 }
  58
  59 static void iothread_instance_finalize(Object *obj)
  60 {
  61     IOThread *iothread = IOTHREAD(obj);
  62
  63     iothread->stopping = true;
  64     aio_notify(iothread->ctx);
  65     qemu_thread_join(&iothread->thread);
  66     qemu_cond_destroy(&iothread->init_done_cond);
  67     qemu_mutex_destroy(&iothread->init_done_lock);
  68     aio_context_unref(iothread->ctx);
  69 }
  70
  71 static void iothread_complete(UserCreatable *obj, Error **errp)
  72 {
  73     IOThread *iothread = IOTHREAD(obj);
  74
  75     iothread->stopping = false;
  76     iothread->ctx = aio_context_new();
  77     iothread->thread_id = -1;
  78
  79     qemu_mutex_init(&iothread->init_done_lock);
  80     qemu_cond_init(&iothread->init_done_cond);
  81
  82     /* This assumes we are called from a thread with useful CPU affinity for us
  83      * to inherit.
  84      */
  85     qemu_thread_create(&iothread->thread, "iothread", iothread_run,
  86                        iothread, QEMU_THREAD_JOINABLE);
  87
  88     /* Wait for initialization to complete */
  89     qemu_mutex_lock(&iothread->init_done_lock);
  90     while (iothread->thread_id == -1) {
  91         qemu_cond_wait(&iothread->init_done_cond,
  92                        &iothread->init_done_lock);
  93     }
  94     qemu_mutex_unlock(&iothread->init_done_lock);
  95 }
  96
  97 static void iothread_class_init(ObjectClass *klass, void *class_data)
  98 {
  99     UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
 100     ucc->complete = iothread_complete;
 101 }
 102
 103 static const TypeInfo iothread_info = {
 104     .name = TYPE_IOTHREAD,
 105     .parent = TYPE_OBJECT,
 106     .class_init = iothread_class_init,
 107     .instance_size = sizeof(IOThread),
 108     .instance_finalize = iothread_instance_finalize,
 109     .interfaces = (InterfaceInfo[]) {
 110         {TYPE_USER_CREATABLE},
 111         {}
 112     },
 113 };
 114
 115 static void iothread_register_types(void)
 116 {
 117     type_register_static(&iothread_info);
 118 }
 119
 120 type_init(iothread_register_types)
 121
 122 IOThread *iothread_find(const char *id)
 123 {
 124     Object *container = container_get(object_get_root(), IOTHREADS_PATH);
 125     Object *child;
 126
 127     child = object_property_get_link(container, id, NULL);
 128     if (!child) {
 129         return NULL;
 130     }
 131     return (IOThread *)object_dynamic_cast(child, TYPE_IOTHREAD);
 132 }
 133
 134 char *iothread_get_id(IOThread *iothread)
 135 {
 136     return object_get_canonical_path_component(OBJECT(iothread));
 137 }
 138
 139 AioContext *iothread_get_aio_context(IOThread *iothread)
 140 {
 141     return iothread->ctx;
 142 }